Frog Dissection Why do we dissect frogs?

Main Menu Terminology Background Information Materials External Anatomy Inside the Mouth Procedure Copy of Worksheet Concept Map Author’s information Resources

Terminology Dorsal-on or near the back Ventral-on or near the front (opposite of dorsal) Posterior-on or near the behind Anterior-on or near the top

Background Information Click on this video to learn about the environmental threats on frogs Click on this video to learn about frogs skin and its qualities

Materials A dissecting tray Pins A frog Scalpel Scissors Forceps

External Anatomy Identify: Take notice of the skin The external Nares (nostrils) The eyes and the third eye-lid (which covers the eye when underwater. Locate the Tympanic membrane (ear drum) just posterior to the eye. Locate the shoulder, elbow, and wrist joints of the Forelimbs. How many Digits (fingers) are there to a Forelimb? At the posterior end of your frog is the Cloaca (feces, urine, and reproductive cells are expelled here). Examine the muscular hindlimbs Locate the thigh, knee, and ankle joints Examine the webs of the foot. How many Digits are there to each hindlimb?

Inside the Mouth Identify: Two large Muscular Pads are in the roof of the mouth (eyes retract here when it blinks) Locate Tongue. What unusual features do you notice? Find the two knobs that come out of the roof of the mouth. These are called Vomerine teeth. Rub your finger along the inside of the jaw, you will feel the maxillary teeth.

Procedure Click here to watch video Examine the exterior of the frog. (Follow the External Anatomy and Inside the Mouth slides) After answering the questions on the exterior, placing the frog on the tray ventral side up. Pin the forelimbs and hindlimbs to the tray. Make a cut down through the middle of the frog and then two perpendicular cuts (watch the video showing the process). Click here to watch video After you make your cut, pin the skin back to the tray, now repeat the process and cut through the muscle layer this time (exposing the internal organs). Go to next slide for further procedures…

Procedure…2 Internal Anatomy Answer the appropriate questions on the worksheet as you go along. Carefully find the liver (large brown organ with 3 lobes) and remove it. Your frog may have fat bodies and if you have a female it may contain a mass of eggs (you may need to remove these in order to examine the organs). Find and remove : the stomach, intestines, pancreas (yellowish color), and gall bladder (greenish color). the heart, left lung, and right lung. the spleen and kidneys. the ovaries (female) or testes (male) Go to the next slide for further procedures…

Procedure…3 Internal Anatomy After removing the necessary organs, unpin the frog and turn it dorsal side up. You are going to cut the skin on the neck and head to expose the cranium. Then cut open the cranium and expose the brain. Dispose of the frog and materials as directed in class. Clean all tools appropriately.

Copy of the Worksheet worksheet will be given out in class 1. Write down your observations of the skins texture and color. 2. Look at the hind limbs…there are __ toes on each foot. 3. Look at the front limbs…there are __toes on each foot. 4. When looking at the tongue, where is it attached (the back or front of the mouth)? 5. Is your frog male or female? How did you know it was male/female? Click next to continue to page 2 of the worksheet

Copy of Worksheet…2 6. What is the livers function in the body? 7. Follow the digestive tract of the frog and briefly explain who food goes from the mouth and out of the anus. 8. There are __ chambers in the heart. 9. What is the small green sac that attaches to the liver? 10. Examine the cranium and brain, describe what you see.

Tympanum Lungs External Nares Liver Internal Nares Gall Bladder Maxillary Teeth Stomach Vomerine Teeth Small Intestine Eustachian Tubes Large Intestine Tongue Spleen Esophagus Kidney Glottis Oviducts/Eggs Heart Testis

Tympanum The tympanum, found just behind the eyes, functions as the ears of the frog. They receive sound waves both above and below water allowing the frog to hear. Home

External Nares The nares primary role is to let air into and out of the frog. This is a view of the nares from outside of the frog. Home

Internal Nares The nares primary role is to let air into and out of the frog. This is a view of the nares from inside of the frog. Home

This set of teeth is used for holding prey. Maxillary Teeth This set of teeth is used for holding prey. Home

This set of teeth is also used for holding prey. Home Vomerine Teeth

The eustachian tubes function to equalize pressure on both sides of the eardrum or tympanum Home Eustachian Tubes

Tongue The tongue aids in swallowing and catching prey. In humans the tongue also aids in speech and taste. Home

Glottis The glottis is the opening between the vocal chords at the upper part of the windpipe or larynx. Home

Esophagus Food is swallowed through the esophagus where peristalsis aids its movement to the stomach. Home

Lungs The lungs transport oxygen to the blood as well as remove waste like carbon dioxide through a process called respiration. Home

Heart Unlike the human heart the heart of a frog only has three chambers (two atria and one ventricle) however the role and function is the same. The heart pumps blood throughout the body carrying oxygen and nutrients and picking up waste to be filtered by other parts of the body. Home

Large Intestine The main role of the large intestine is to absorb water and store fecal material until it can be excreted from the body. Home

Small Intestine The small intestine receives the mixture of chyme from the stomach through the pyloric valve. In the small intestine nutrients are absorbed from the tiny villi lining the inner walls of the small intestine. Home

Stomach In the stomach food is further broken down by gastric juices and peristalsis until it becomes a liquid substance called chyme. Home

Liver The liver produces bile, a substance that emulsifies fats contained within the food we eat, and stores it in the gall bladder to be secreted into the small intestine. Home

Gall Bladder The gall bladder stores bile that is received from the liver. Bile is secreted from the gall bladder into the first section of the small intestine (duodenum) to help aid in digestion. Home

Spleen The spleen helps to destroy old red blood cells and lymphocytes, which are cells that produce antibodies to help fight infected and cancerous cells. Home

Kidneys The Kidneys filter out waste from the blood through structures known as nephrons. The waste removed is combined with water to form urine. Home

Oviducts & Eggs The oviducts are tubes that carry eggs from the ovaries to the uterus. The eggs are the female reproductive cell. Home

Testis The testis are the male reproductive gland that produce sperm and male hormones such as testosterone. Home

Tympanum Lungs External Nares Liver Internal Nares Gall Bladder Maxillary Teeth Stomach Vomerine Teeth Small Intestine Eustachian Tubes Large Intestine Tongue Spleen Esophagus Kidney Glottis Oviducts/Eggs Heart Testis

Resources Video of Frog Dissection http://www.youtube.com/watch?v=vK-YTwHZTSY Red Eyed Tree Frog Pictures animals.nationalgeographic.com Video of Frog Skin and Video of Environmental Threats http://www.unitedstreaming.com